Poly-n-vinyl lactam photographic silver halide emulsions



Patented Jan. 31, 1950 POLY-N-VINYL LACTAM PHOTOGRAPHIC SILVER HALIDEEMULSIONS Elmer Keiser Bolton, Wilmington, DeL, assignor to E. I. duPont de Nemours & Company, Wilmington, DeL, a corporation of Delaware NoDrawing. Application August 28, 1948, Serial No. 46,722

8 Claims. (01. 95-7) This invention relates to photographic emulsionsand emulsion layers composed of polymers of poly-N-vinyl lactams and tophotographic elements containing such emulsion layers.

Many different materials have previously been used in photographicemulsions as binding agents for light-sensitive components. The mostwidely used material, gelatin, is well adapted to this use because itserves as a good protective colloid for silver halides in such emulsionsand, when coated ona suitable support, these emulsions form films whichare permeable to the aqueous solutions used to develop photographicimages. Gelatin has a number of disadvantages, however, among which maybe mentioned its high cost, lack of uniformity of one batch withanother, susceptibility to bacterial attack, and its susceptibilit tochange in physical properties with changing humidity conditions.

It has now been found that useful photographic compositions can be madeby incorporating lightsensitive material capable of forming a latentimage, and especially silver halides, in a poly-N- vinyl lactam havingan average molecular weight of about 10,000 to 500,000. This may beaccomplished by dissolveding the poly-N-vinyl lactam in water andadmixing the light-sensitive silver halidetherewith. After thelight-sensitive material has been uniformly dispersed, the resultingcolloidal dispersion may be further modified and coated on a support toform alight-sensitive layer.

In a practical mode of procedure, the poly-N- vinyl lactam, e. g.,poly-N-vinyl caprolactam, is dissolved in water. Separate solutions aremade by dissolving a soluble, ionizable halide, e. g., sodium,potassium, or ammonium chloride, bromide, or iodide, and b dissolveingseparately in water a soluble, ionizable silver salt, e. g., silvernitrate. The three solutions thus formed are mixed simultaneously todisperse colloidally lightsensitive silver halide in the polymer. Theresultir'ig emulsion can then be ripened, chilled, coagulated ,andwashed. Unwashed emulsions can be used but, 'in general, it is desirableto remove the excess s'oluble salts, preferably by dialysis. Theprecipitate can then be redispersed and the emulsion modified by theaddition of more of the same type of poly-N-vinyl lactam, generalemulsion sensitizers, anti-fogging agents, spectral sensitizing dyes,preservatives, hardeners, and/or color formers and coated on a temporaryor permanent support or on a layer of such support.

After the light-sensitive poly-N-vinyl lactam solution is prepared forcoating, it may be deposited in the same .Way that gelatin-silver halidesolutions are'coated upon a suitable support, e. g., metal, paper,glass,"or a transparent film such as a cellulose derivative, e. g.,cellulose nitrate, cellulose acetate, or a superpolymer, e. g.,polyvinyl chloride, polyethylene, nylon, etc., and dried. The resultingelement can then be exposed and processed to positive or negativepictures in the same manner as ordinary gelatino-silver halidephotographic elements.

The poly-N-vinyl lactams which have been found to be useful in thephotographic emulsion layers of this invention can be made by adding afree radical producing catalyst, e. g., p-tertiary butyl peroxide,ma-azo-bis-isobutyronitrile, etc, to N-vinyl lactams, e. g., N-vinylcaprolactam, and heating in the absence of oxygen until the polymer isformed. The useful poly-N-vinyl lactams have an average molecular weightof about 10,000 to 500,000 and are generally soluble in Water at 5 C. to25 C. to the extent of 5%-20% or more. They can, however, be dissolvedin watercontaining small amounts (l0%-20%) of a water-soluble organicsolvent, e. g., ethanol or methanol. The polymerization of N-vinylcaprolactam with a -azo-bis-isobutyronitrile and related catalysts isdisclosed and claimed in Hunt U. S. application Ser. No. 655,015, filedMarch 16, 1946, now abandoned, and continuation-in-part application Ser.No. 2,551, filed January 15, 1948, now Patent No. 2,471,959.

The invention is further illustrated by the following examples in whichparts are by weight. The photographic solutions and coatings wereprepared in the absence of actinic light or radiations.

Example l A photographic emulsion containing poly-N- vinyl caprolactamhaving an average molecular weight of about 40,000 as the binder forsilver hal ide was prepared as follows: Separate aqueous solutionscontaining the following constituents were made. Y

3 These three solutions were mixed simultaneously by running streams ofsolutions A and B from separate containers into a common reaction vesselcontaining solution C with rapid agitation. The resultinglight-sensitive silver halide suspension in the poly-N-vinyl caprolactamwas :dialyzed through a water-permeable cellophane (regeneratedcellulose) membrane having a thickness .of about 0.8 mil. until theconductivity had been reduced to 800 micromhos and coatings were made onraw stock paper coated with baryta gelatin. After drying, thephotographic element was exposed by focusing on it the imageo'f'atransparency negative and developed by immersion at 20 C. in a standardp-methylaminophenolhydroquinone developer having the followingcomposition:

Parts p-Methylaminophenol sulfate .3.1 SOdiumsulfite (anhydrous) 34510Hydroquinone 121) Sodium carbonate (anhydrous) 67,5 Potassium bromide1;9

Water to make 1,000

.The developed picture was fixed by bathing in 1a. 25% solution ofsodium vthiosulfate, freed from soluble salts by washing, andthen-dried. .The re- ;sulting black and white picture had densitygradations complementary to the object .scene to which the element wasexposed. The developed picture formed from the :poly-N-yinyl caprolaotamshowed 'speed, contrast, and fog-values comparable to that ofcommercial:gelatino-silverihalide emulsionsused onenlarging'papers.,Printszon paper of this emulsion have a pleasingiwarmth :of :tone.

Similarly, a photographic emulsion can .be prepared in whichpoly-.N-vinyl caprolactamzisused .as abinder forlight-sensitive:silver'halideand a .color former. After exposing andprocessing .-in the usual.manner witha color developer-containingN-p-diethylaminoaniline, a photographic :element bearing a coloredphotographic image ,can be obtained.

Example II A photographic emulsion containing poly-N- vinyl-butyrolactamas the :binderfor silver halide was prepared -.as :follows: Separateaqueous solutions containing the following components .were made.

A AgNOs (3N) cc s5 NHOH (20%) cc 35 NHdBl :(BN) ..-gcc, .37 KI ,(O.5Ncc... \6 10% soln. of poly-N-vinylbutyrolactam (average molecular weightof about 60,000) grams 120 4 valerolactam. Mixtures of two or more ofsuch lactams can be used. The poly-N-vinyl lactams should be capable ofallowing the photographic processing solutions to penetrate suflicientlyto act on the exposed and unexposed light-sensitive sil- -ver halide; atthe same time, they should not dissolve in photographic processingsolutions. To

achieve this, they must have an average molecular weight of 10,000 to500,000 or above.

invention is not limited to the specific light-sensitive silver halidesdescribed in the above examples. Various other simple and mixed silverhalides may be used as the light-sensitive materials of this invention.Mixtures of silver chlorides, bromides, and/or iodides can be made sbyadding mixtures of soluble salts of these halides in the same manner asdescribed in Example I. Other useful soluble halides include potassiumbromide, sodium iodide, sodium and potassium chlorides, etc.

.The :poly-N-vinyl lactams are useful :not only :as the binding agentfor light-sensitive silver salts in radiation sensitive layers but may'alsobeused .as a water-permeable binder for other light-sensiitivematerials capable of forming a latent image such as diazonium compounds,ammonium bichromate, fu-lgides, *N-monoarylhydroxylamincs and their-nitrones, etc. 'They-mayalso be used as :the binding agent of filterlayers which may have .dyes dispersed therethrough or antihalation layers which :have antihalation dyesor pigments dis- .persed therethrough,.and .as binding agents for non diffusing.coloiflformers which areplaced adijacent to light-sensitive silver halide layers.

To the emulsions after formation and digestion can ;be added. eitherduring :the digestion stage or before, various types :of sensitizingagents, e. g., sulfur sensitizers such as 'allyl ithioureas,thiocyanates, :or sodium thiosuliate. In addition-various types ofoptical sensitizing dyes which modii y the spectral characteristics ofthe resulting emulsion can be added.

Various "types of color formers -or dye intermediates capable of forming'quinoneimine,

* indophenol or azomethine dyes on color-forming development can beincorporated in the emulsions. -Thus, the phenols, naphtho'ls,pyrazolones, 'acyl'acetamides, hydrindene, EN-

=homophthalimides, etc., particularly those '01 high molecular weightand which are immobile in gelatin emu'lsion layers can be 'used.Suitable color formers are described in United States Patents 2,108,602,2,166,181 2,178,612, 2,179,228,

* 2,179,238, 2,179,239, 2,182,815, '2,1s4,303,-2,1ss,s49,

2,200,924, 2,283,276, and "2,328,652.

As compared with gelatin emulsions prepared under comparable conditionsthe poly-N vinyl lactam emulsions contain 'smaller size particles ofsilver halide and, therefore, 'give emulsions films, in lithographicfilm, and asportraitrma- 'teria'ls. "Infa-ctthe'illm elements of'thisinvention can be used in systems in which elements based on gelatinor collodion have been used.

What is claimed is:

1. A photographic emulsion comprising lightsensitive silver halidegrains dispersed in a poly- N -vinyl lactam having a molecular weight ofabout 10,000 to 500,000.

2. A photographic emulsion comprising lightsensitive silver halidegrains dispersed in a poly- N-vinyl lactam having from 4 to 6 carbonatoms in the lactam ring and a molecular weight of about 10,000 to500,000.

3. A photographic emulsion comprising lightsensitive silver halidegrains dispersed in a poly- N-vinyl caprolactam having anaverage-molecular weight of about 10,000 to 500,000.

4. A photographic element comprising a support bearing a photographicemulsion comprising light-sensitive silver halide grains dispersed in apoly-N-vinyl lactam having a molecular weight of about 10,000 to500,000.

5. A photographic element comprising a sup port bearing a photographicemulsion comprising light-sensitive silver halide grains dispersed in apoly-N-vinyl lactam having from 4 to 6 carbon atoms in the lactam ringand a molecular weight of about 10,000 to 500,000.

6. A photographic element comprising a support bearing a photographicemulsion comprising light-sensitive silver halide grains dispersed in apoly-N-vinyl caprolactam having an average molecular weight of about10,000 to 500,000.

7. A photographic element comprising a transparent film support bearinga photographic emulsion comprising light-sensitive silver halide grainsdispersed in a poly-N-vinyl lactam having from 4 to 6 carbon atoms inthe lactam ring and a molecular weight of about 10,000 to 500,000.

8. A photographic element comprising a transparent film support bearinga photographic emulsion comprising light-sensitive silver halide grainsdispersed in a poly-N-vinyl caprolactam having an average molecularweight of about 10,000 to 500,000.

ELMER KEISER BOLTON.

No references cited.

1. A PHOTOGRAPHIC EMULSION COMPRISES LIGHTSENSITIVE SILVER HALIDE GRAINSDISPERSED IN A POLYN-VINYL LACTAM HAVING A MOLECULAR WEIGHT OF ABOUT10,000 TO 500,000.